1. Field of the Invention
The invention relates to a transparent roof module for a motor vehicle roof. In particular, the present invention relates to such a transparent roof module including solar cells.
2. Description of Related Art
Published German patent application DE 37 25 053 A1 discloses a motor vehicle glass roof with an outside first glass pane made from flint glass in which a smaller glass pane adapted to absorb part of the incident solar energy is provided in a first partial area above a viewing opening formed in the bottom of the solid roof skin in a sandwich-like construction, and is provided with solar cells in a second partial area on a bottom surface which is above a solid roof part. The disadvantage in the disclosed motor vehicle glass roof is the fact that the glass roof is expensive to fabricate and is very heavy.
Published German patent application DE 196 30 813 A1 discloses a pane structure which, for example, can be used for the cover of a sliding motor vehicle roof and consists of a composite of an outer larger glass pane and an underlying inner smaller glass pane. In the overlapping area between the panes, there is provided an electrochrome layer structure in order to control the transmission of the pane structure. The outer glass pane is coated before assembly with some of the electrochrome layer structure. In the edge area of the outer pane in which the panes do not overlap, the outer glass pane is provided with solar cells on the bottom surface. The disadvantage of this disclosed pane structure is that it is very expensive to fabricate.
Published German patent application DE 37 13 854 discloses a motor vehicle roof with a roof opening which can be closed by two movable covers in a fixed roof panel, the front cover which is made as a sliding and lifting cover consisting essentially of a pane of transparent material which is provided with solar cells in its edge area which is designed to prevent viewing of the cover mechanism from above. The central portion of a movable cover which allows viewing is provided with solar cells which are arranged in a lattice to reduce the incident solar radiation into the vehicle interior. The disclosed motor vehicle roof is also disadvantageous in that its fabrication is complicated.
One object of the present invention to provide a transparent roof module which allows efficient utilization of solar energy.
Another object of the present invention is to provide such a transparent roof module which provides a high level of comfort for the passengers.
Still another object of the present invention is to provide such a transparent roof module which minimizes weight.
Yet another object of the present invention is to provide such a transparent roof module which can be easily and economically produced.
In accordance with the preferred embodiments of the present invention, these objects and others are achieved by providing a transparent roof module for a motor vehicle roof where the transparent roof module includes a transparent pane for covering a roof opening, the cover including a nonviewing area and a viewing area through which objects are viewable through the cover, a transmission reducing layer provided on the viewing area of the transparent pane for reducing transmission of at least one of infrared and visible spectral range through the viewing area and solar cells provided at the nonviewing area of the transparent pane.
The transparent roof module in accordance with the present invention advantageously provides solar cells which are located only in areas of the transparent pane which cannot be used for viewing, i.e. the nonviewing areas which do not contribute to comfort with respect to light incidence. In addition, in the preferred embodiment of the present invention, the transparent roof module prevents excess light incidence and excess heating of the vehicle interior by infrared radiation while at the same time, incident solar radiation onto the solar cells is not reduced. In this regard, the transmission in the viewing area is reduced by applying of film and/or coating to the transparent pane. This allows the transparent roof module in accordance with the present invention to be easily and economically produced without significantly increasing the weight of the transparent roof module.
In one preferred embodiment of the present invention, solar cells are provided at all surface areas of the transparent pane which by virtue of the construction cannot be used to view objects beyond the transparent pane from the vehicle""s interior, i.e., the nonviewing areas. In this regard, all other surface areas, i.e. the viewing areas, are provided with the transmission-reducing coating and/or film. This allows very efficient use of solar energy, especially when the pane is made of clear glass, while attaining maximum comfort for vehicle occupants and allowing easy manufacture of the transparent roof module.
In another preferred embodiment of the invention, the transmission reducing layer is made as black ceramic printing with spots or hole filters. This is an especially simple and economical approach for providing a transmission reducing layer.
Alternatively, the transmission reducing layer may a colored polycarbonate film which is laminated to a bottom surface of the transparent pane with adhesive film. This approach allows easy manufacturability and reduced weight.
The transmission reducing layer can also be a metal oxide coating which is applied to the bottom surface of the transparent pane. This approach also allows easy manufacturability and extremely low weight. This approach further minimizes any visible transitions of the transparent plane.
In addition, a colored transparent polycarbonate film may also be laminated onto the metal oxide coating by an adhesive film. In this way, transmission properties are achieved in a similar manner to colored glasses and the coating is protected from corrosion.
Furthermore, the transmission reducing layer may also be a dark tail film which is coated to be scratch-resistant and is cemented directly to a bottom surface of the transparent pane with acrylate cement. This approach is particularly advantageous in that it is substantially scratch proof.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the invention when viewed in conjunction with the accompanying drawings.